The error layout wrongly informs the user that another video is about to play when sending multiple unsupported video to the player

[SoftVision-CarmenFat]

[Affected versions]:

• Firefox Developer Edition 59.0b4
• Firefox Nightly 60.0a1 (01/29/2018)
• Min-Vid Shield Study Onboarding 0.4.7 - Shield Study

[Affected Platforms]:

• All Windows
• All Linux
• All Mac

[Prerequisites]:

• Latest Min-Vid v.0.4.7 Shield Study Onboarding ("active" or "activeAndOnboarding" variant) was previously installed on a clean profile.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites.
2. Navigate to www.youtube.com website.
3. Send an unsupported video to the Player.
4. Send an unsupported video to the Player again and observe the error layout.

[Expected result]:

• Multiple videos can't be sent to the player (see issue #1213), therefore, the notation that informs the user which is the next video that is about to be played shouldn't be displayed.

[Actual result]:

• The notation that informs the user which is the next video that is about to be played is displayed.

[Notes]:

• Attached a screenshot of the issue: